The La Palma volcano, which erupted five days ago, has entered its most explosive phase so far. The intensity with which ashes and pyroclasts have begun to come out of its interior has forced the cancellation of flights at the airports of La Palma and La Gomera and the evacuation of the residents of Tajuya, Tacande de Abajo and the part that was not evacuated from Tacande de Arriba. The authorities have also evicted journalists who were narrating what happened in the area.
The experts consulted assure that, in strombolian-type volcanoes, the “valley” and “peak” phases of the eruptive activity “are normal” but also difficult to “predict accurately”. The greatest risk is now concentrated not so much in the lava flows, but in the pyroclasts – lava fragments – that expel the volcano’s mouths at a great distance and in the expansive wave that the earthquake generates in the buildings, explains José Luis Barrera, volcanologist from the College of Geologists, in conversation with elDiario.es. “It is not known what explosions will be in ten minutes. Evicting is a wise move,” he adds.
The National Geographic Institute has verified an exponential increase in the tremor through its measurement in a seismic station close to the eruption until late Friday afternoon. Afterwards, it has been reduced. The graph attests to the behavior of peaks and valleys that scientists explain.
But why does the explosive intensity change? “If the amount of gases varies, if the characteristics of the magma change, its temperature changes, its viscosity changes, or if any of its parameters change, then inside the chimney the explosions can be more or less violent and what comes out the air is more or less amount of ash “, explains María José Huertas, a petrologist from the Department of Petrology and Geochemistry of the Faculty of Geological Sciences of the Complutense University of Madrid.
The expert also insists that “it is very difficult to know” how long a more explosive phase can last or when volcanic activity will cease. To make a calculation, only the records are useful, which indicate that the volcano could continue expelling lava between 24 and 84 days. “At any moment a new course of cooler magma can come that fills the chamber and that feeds itself and a more explosive cycle takes place again, as if we were going back to the starting box”, adds Huertas.
Regarding the most explosive phases of the volcano, Huertas comments that it may be due to the lava having encountered an obstacle, to contact with gases or to running into water. According to Barrera, the white clouds indicate that the magma has come into contact with the water. “It is a very alive process. For an hour everything may be changing continuously. It is a very dynamic thing. That the gases change, that a piece of rock falls or I do not want to tell you anything if it meets water on top [como en Islandia]”completes Huertas.
The volcano will be inactive when the conduit through which the eruptive column with the ash and the fire sources is currently emerging is clogged. “The conduit at the moment, so to speak, is empty because the lava is coming out, when what remains inside ceases it will end up cooling and consolidating.” Knowing when this will occur is anyone’s guess.